Time Allotment: 3 Class Days
The purpose of this lab is to perform measurements capable of determining the power rating of our own legs in lifting our bodies up a flight of stairs and to relate our understanding of power to the ability of other humans and machines to do work in a specified amount of time.
All machines are typically described by a power rating. The power rating indicates the rate at which that machine can do work upon other objects. Thus, the power of a machine is the work/time ratio for that particular machine. To determine the power of a machine, one must be able to calculate the work done by the machine (through knowledge of the force it applies to displace an object) and the time it takes to do this amount of work.
A person is a machine which also has a power rating. Some people are more power-full than others; that is, they are capable of doing the same amount of work in less time. In this lab you will measure your own personal power by making measurements as you climb up a flight of stairs within your home. Additionally, you will perform one other activity in which you measure the power of your wrists, arms, etc.
In order to accomplish the purpose of this lab, it would be useful to begin analyzing the physical situation which you will be investigating. Thus, before proceding with the measurements and calculations, answer the following questions.
1. In the space at the right, construct a free-body diagram showing all the forces acting upon your body as you climb up one flight of stairs at a constant speed. Label the forces according to type.
2. Discuss how you will be able to measure the upward force applied to your body as you climb the stairs at a constant speed. (HINT: 1 kg of mass on Earth is equivalent to 2.2 pounds of weight.)
3. Write two equations - one for the work done upon your body as you climb the stairs and one for the power generated by your body.
4. Make a list of all the quantities which need to be measured in order to determine your personal power as you elevate your body up a flight of stairs.
Once you have established a good understanding of the measurements which need to be made, set up a data table, make measurements, and procede to calculate the power output of your body as you rapidly climb up a flight of stairs in your home. Use a ruler to determine the height of the stairs (Note: 12 in = 1 ft and 3.28 ft = 1.0 m). Use a stopwatch to determine the time.
Record all measured and known data below.
Calculate your power in the space below. PSYW
Express your understanding of the concept and mathematics of power by answering the following questions. Observe that some problems require you to determine the speed resulting from the power output of a person or machine. Consult the equation in your packet for such problems. Show all your work in an organized fashion.
Write a conclusion which relates to the purpose of this lab.
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This page created by Tom Henderson and last updated on 12/4/97.